The invention relates to spray apparatus primarily for use in agriculture, although such apparatus may find application in horticulture or in industry generally.
Circulation in the boom spray lines of agricultural crop spray apparatus has become an increasingly important part of the modern machine. Inventions such as that known by the trade name LASER, see EP 0 820 224 B1 and sold by Knight Farm Machinery Limited and which concern the agitation of spray liquid in the spray lines to provide a simple addition to a standard sprayer or the more conventional pressurised circulation systems, are well known.
Spray line circulation was one of the early building blocks towards a modern sprayer design that is now increasingly influenced by environmental considerations.
One very significant area of concern is in the volume of spray liquid retained within the spray apparatus when the sprayer stops working. This is known as sprayer retained volume or SRV. Typically this could be as much as 100 liters or more. Recent work has been done to significantly reduce this by condensing the plumbing system of the sprayer and reducing the number of components. Today SRV can be as low as 20 liters on some machines but more typically would be around 50 liters.
Customers continue to ask for wider booms which obviously have to be fitted with spray lines. This results in more pipe-work and forces SRV upward. Any recirculation system adds to the pipe-work and increases the problem further.
With booms now being built up to 48 m in width, there are also pressure losses in the pipe-work that can affect the chemical output across the boom. This calls for bigger pipe-work, which increases retained volumes.